Triangle properties and Heron’s formula
A triangle is valid only if the sum of any two sides is strictly greater than the third side. When this condition is met, Heron's formula can determine the area of the triangle without knowing its height.
Heron's formula uses the semi-perimeter (half the perimeter) and side lengths: Area = sqrt(s(s-a)(s-b)(s-c)). It is highly useful in land measurement, construction, and geometry studies.